1. Field
One embodiment of the present invention relates to a wiring board which suppresses increased area, a method of designing the wiring board, and an electronic apparatus.
2. Description of the Related Art
Design of wiring boards has become difficult with increased frequency. When the output impedance of an IC driver is the same as the characteristic impedance of the transmission line, no reflection noise occurs. However, adjusting the impedance of the transmission line to obtain impedance matching increases the width of the line. Although there is also a method of obtaining impedance matching by inserting a damping resistor or the like, it is necessary to insert the resistor close to the IC driver, and provide wiring on the surface of the wiring board for part mounting. These cause problems of increased area of the wiring board and increased cost of parts.
Jpn. Pat. Appln. KOKAI Pub. No. 2001-127192 discloses a semiconductor device mounting board, in which a line drawn from an electrode pad is made narrow and has a length not influenced by reflection due to impedance mismatching, and lines in other parts are made heavy.
As described above, when the impedance of the transmission line is adjusted to obtain impedance matching, the wiring width is increased, and so the area of the wiring board is increased. Further, inserting a damping resistor or the like to obtain impedance matching increases the area of the wiring board and increases the cost.
In addition, the above document fails to disclose the specific length not influenced by reflection due to impedance mismatching.